In the manufacture of stator and rotor cores for dynamoelectric machines, it is common practice to build these cores from a series of punched laminations. The laminations are assembled in abutting relationship to each other in a stack that runs axially along the machine. The axial ends of the stack of laminations are closed off by end plates which provide compression forces to the laminations. The laminations are typically provided with a plurality of through holes which also extend through the end plates. Through bolts or core studs typically pass through the through holes of the laminations and the end plates. The core studs have end portions which extend beyond the end plates. The core stud end portions are usually threaded to receive nuts and other washers which when tightened press against the end plates to provide axial tightness of the core assembly.
It is also known to electrically insulate the laminations in the core from each other by coating the laminations with an inorganic insulated material so that there is no current that would normally pass between the laminations. To prevent electrical losses through the core and the core studs, it is known to insulate the core studs. Typically, this insulation comprises taping of the core studs or painting the core studs with an insulated material. However, the electrical insulation between the laminations and core studs may be compromised when the core studs are inserted into the through holes in the laminations. The problem is that the through holes provide relatively sharp edges of metal or iron that may shred or cut into the insulation of the core stud. Consequently, electrical shorting may occur from the laminations through the core stud.
U.S. Pat. No. 4,494,030 issued Jan. 15, 1985 to Mulach et al. shows a stator core structure for a dynamoelectric machine having a plurality of core studs that extend through the laminations. In addition to these core studs that extend through the lamination, there is disclosed radial outer core studs that extend through the stepped iron, the finger plate, the end plate and the end shield. These outer core studs are insulated with insulative cylinders that are slipped over the outer core studs in the region of the stepped iron. The insulative cylinders are used in this region to prevent electrical communication between the outer core studs and the end shield. These insulative cylinders are slid over the outer core studs. The cylinders are able to slide relative to the outer core studs and must be held axially in place by additional plate layers at the axial ends of the step iron.
There is a need to provide for insulation affixed to the core stud used in the core assembly of rotors and stators of dynamoelectric machines that provides for protection of the insulation from the laminations during the assembly of the core structure.